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10364Re: [loopantennas] RE: RE: 1.5-volt active loop antenna?

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  • qrp.gaijin
    Jan 1, 2014

      In loopantennas@yahoogroups.com, <christrask@...> wrote:

      > I just deleted that earlier PDF file and replaced it with "Active Antenna Amplifiers for Low Voltage Operation.pdf" that has the low input impedance amplifier on the second page. This is still a work in progress.

      I'm thinking about building the low-input-impedance amplifier on the second page, using 2N3904 transistors and running off of 1.2 volts. Intended use is for shortwave listening and maybe MW listening. A couple of questions:

      1. Are the ferrite beads necessary?

      2. I'm thinking about winding the inductors and transformers as follows. All inductors will be wound on FT50-43 cores. T1: 20 turns, center-tapped. T2: 20 turns primary, 20 turns secondary, each center-tapped. L1: 20 turns. T3: 20 turns primary (center-tapped), 20 turns secondary (output). Do these values sound reasonable?

      3. For Q1-Q4, what base and collector voltages should I aim for?

      4. Is symmetrical physical construction important? 

      5. Why can't we take the antenna output directly off of the T2 secondary, using Q3 and Q4 only and eliminating Q1 and Q2?

      6. I'm planning on using the coaxial cable to supply power to the antenna, using a bias tee and running +Vcc through the T2 secondary (similar to the original M0AYF design). Any problems with this approach?

      Thanks for any advice.

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